ACCEPTED MANUSCRIPT
In a round-bottom flask equipped with a stirring bar and a Dimroth condenser, 2-furyl
chloride (20 g, 0.14 mol), tert-butyl alcohol (160 mL, 1.7 mol) and sodium azide (10.2g,
0
.16 mol) were placed, under argon atmosphere. The mixture was stirred for 12 h at
room temperature and the formation of the intermediate 2-furylazide as a white solid
was observed. The mixture was heated to reflux (100 ºC) and maintained under these
conditions for additional 12 h. Once 2-furoylazide 5 was completely converted (control
by TLC eluted with hexane/ethyl acetate 4:6), the solvent was removed in vacuo,
obtaining a white solid, which was submitted to a flash column chromatography on
silica gel, eluting with a mixture of hexane and ethyl acetate of increasing polarity. The
elution with a mixture of hexane and EtOAc (9:1), afforded the desired product as a
white solid (21.6 g, 82% yield). The product 6 has to be stored in a cold place and away
from light, in order to avoid its thermal or photochemical decomposition.
MP = 98-99 ºC (ethyl acetate). TLC: R = 0.66 (SiO , hexane/ethyl acetate 4:6,
f
2
developed by ninhydrin). IR (film): ῡ = 3267 (N─H, st), 2980, 1700 (C=O, st), 1546
t
-1 1
(
N─H, def), 1250 ( Bu) cm . H NMR (300 MHz, CDCl ): δ = 1.50 (9H, s, H2'), 6.04
3
1
3
(
1H, brs, H4"), 6.63 (1H, brs, H3"), 7.00-7.12 (1H, m, H5") ppm. C NMR (50 MHz,
CDCl ): δ = 28.2 (C2'), 81.3 (C1'), 95.1 (C4"), 111.2 (C3'), 136.0 (C5'), 145.4 (C2'),
3
1
51.9 (C1) ppm. MS (CI, NH , 70 eV, 150 ºC): m/z (%) = 285 (13, M+NH ), 268 (100,
3 4
t
t
M+1H), 212 (22, M+2H‒ Bu), 167 (36, M+1H‒COO Bu).
The intermediate 2-furoylazide 5 could be transformed, one pot, into the
corresponding carbamate 6 without the necessity to isolate it. However, a pure sample
of 5 was isolated and purified for its physical and spectroscopic characterization.
White solid. MP = 114.5-115 ºC. IR (film): ῡ = 3129 (=C-H, st), 2145 (N=N=N, st as),
1
684 (C=O, st), 1562, 1462 (C-N, st), 1393, 1290, 1231, 1190 (C-O-C, st), 1030, 1001,
-1 1
9
16, 877, 793 cm . H NMR (400 MHz, CDCl ): δ = 6.55 (1H, dd, J = 1.6, J = 3,6,
3
4,5
4,3
H4), 7.26 (1H, dd, J = 0.6, J = 3.6, H3), 7.65 (1H, dd, J = 0.6, J = 1.6, H5) ppm.
3
,5
3,4
5,3
5,4
1
3
C NMR (75 MHz, CDCl ): δ = 112.8 (C4), 120.2 (C3), 145.6 (C2), 148.4 (C5), 162.8
3
(
C1') ppm. MS (CI, NH , 70 eV, 150ºC): m/z (%) = 138 (9, M+H), 137 (6, M), 112 (44,
3
M-CN), 110 (100, M-N ), 95 (89, M-N ), 82 (21, M-CN ). TLC: R = 0.60 (SiO ,
2
3
3
f
2
hexane /ethyl acetate 4:6, developed with ninhydrin reagent).
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21 -